Implantable medical devices and methods for making and delivering implantable medical devices

ABSTRACT

Medical devices and methods for making and using medical devices are disclosed. An example medical device may include an implantable medical device. The implantable medical device may include an implantable pacing member having a housing and a lead input. A lead may be coupled to the lead input. The lead may be designed to extend along a pericardial space, epicardium, or both and engage a heart chamber. A passageway may be defined along a portion of the length of the lead.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/804,771, filed on Feb. 28, 2020, which is a continuation of U.S.patent application Ser. No. 16/119,133, filed on Aug. 31, 2018, now U.S.Pat. No. 10,603,487, which is a continuation of U.S. patent applicationSer. No. 14/931,628, filed on Nov. 3, 2015, now U.S. Pat. No.10,092,745, which claims priority under 35 U.S.C. § 119 to U.S.Provisional Application Ser. No. 62/074,863, filed on Nov. 4, 2014, theentirety of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure pertains to medical devices, and methods formaking and using medical devices. More particularly, the presentdisclosure pertains to implantable leads.

BACKGROUND

A wide variety of intracorporeal medical devices have been developed formedical use. Some of these devices include guidewires, catheters,implantable leads, and the like. These devices are manufactured by anyone of a variety of different manufacturing methods and may be usedaccording to any one of a variety of methods. Of the known medicaldevices and methods, each has certain advantages and disadvantages.There is an ongoing need to provide alternative medical devices as wellas alternative methods for manufacturing and using medical devices.

BRIEF SUMMARY

This disclosure provides design, material, manufacturing method, and usealternatives for medical devices. An example medical device may includean implantable medical device. The implantable medical device comprises:

an implantable pacing seed having a housing and a lead input;

a lead coupled to the lead input;

wherein the lead is designed to extend along a pericardial space,epicardium, or both and engage a heart chamber; and

wherein a passageway is defined along a portion of the length of thelead.

Alternatively or additionally to any of the embodiments above, thepassageway is a guidewire lumen that extends between a distal opening ata distal end of the lead and a port positioned proximal of the distalend of the lead.

Alternatively or additionally to any of the embodiments above, thepassageway extends between a closed distal end of the lead and a portpositioned proximal of the closed distal end of the lead.

Alternatively or additionally to any of the embodiments above, the leadis fixedly attached to the lead input.

Alternatively or additionally to any of the embodiments above, the leadis detachably connected to the lead input.

Alternatively or additionally to any of the embodiments above, a guidingmember is disposed within the delivery passageway.

Alternatively or additionally to any of the embodiments above, theguiding member is a guidewire.

Alternatively or additionally to any of the embodiments above, theguiding member is a removable stylet.

Alternatively or additionally to any of the embodiments above, the leadincludes a pre-formed bend.

Alternatively or additionally to any of the embodiments above, the leadincludes an anchoring member designed to anchor the lead to a targetlocation.

An implantable medical device assembly is also disclosed. Theimplantable medical device comprises:

a guidewire capable of being disposed within a pericardial space;

a delivery catheter disposed along the guidewire, the delivery catheterhaving a lumen formed therein;

a pacing lead disposed within the lumen;

wherein the lead has a delivery passageway formed along a portion of thelead;

an implantable pacing seed coupled to the lead, the pacing seed beingdesigned for subcutaneous implantation; and

an imaging device positioned adjacent to the delivery catheter.

Alternatively or additionally to any of the embodiments above, the leadis fixedly attached to the pacing seed.

Alternatively or additionally to any of the embodiments above, the leadis detachably connected to the pacing seed.

Alternatively or additionally to any of the embodiments above, thedelivery passageway is a guidewire lumen that extends between a distalopening at a distal end of the lead and a port positioned proximal ofthe distal end of the lead.

Alternatively or additionally to any of the embodiments above, theguidewire is capable of extending through the delivery passageway.

Alternatively or additionally to any of the embodiments above, thedelivery passageway extends between a closed distal end of the lead anda port positioned proximal of the closed distal end of the lead.

Alternatively or additionally to any of the embodiments above, aremovable stylet is positioned within the delivery passageway.

Alternatively or additionally to any of the embodiments above, the leadincludes a pre-formed bend.

Alternatively or additionally to any of the embodiments above, the leadincludes an anchoring member designed to anchor the lead to a targetlocation.

A method for implanting a medical lead is also disclosed. The methodcomprises:

positioning a guidewire within a pericardial space of a patient;

advancing a delivery catheter along the guidewire;

advancing a lead through the delivery catheter, the lead being coupledto a pacing seed;

wherein a delivery passageway is defined along a portion of the lengthof the lead; and

anchoring the lead to a heart chamber.

The above summary of some embodiments is not intended to describe eachdisclosed embodiment or every implementation of the present disclosure.The Figures, and Detailed Description, which follow, more particularlyexemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of thefollowing detailed description in connection with the accompanyingdrawings, in which:

FIG. 1 is a plan view of an example medical device implanted within apatient;

FIG. 2-5 illustrate portions of example methods for implanting animplantable medical device;

FIG. 6 is a side view of an example implantable medical device;

FIG. 7 is a side view of an example implantable medical device;

FIGS. 8-11 illustrate an example method for implanting an implantablemedical device;

FIG. 12 illustrates a portion of an example implantable medical device;and

FIG. 13 illustrates an example anchoring member for anchoring animplantable lead.

While the disclosure is amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit the invention tothe particular embodiments described. On the contrary, the intention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the disclosure.

DETAILED DESCRIPTION

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere inthis specification.

All numeric values are herein assumed to be modified by the term“about”, whether or not explicitly indicated. The term “about” generallyrefers to a range of numbers that one of skill in the art would considerequivalent to the recited value (e.g., having the same function orresult). In many instances, the terms “about” may include numbers thatare rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numberswithin that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and5).

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

It is noted that references in the specification to “an embodiment”,“some embodiments”, “other embodiments”, etc., indicate that theembodiment described may include one or more particular features,structures, and/or characteristics. However, such recitations do notnecessarily mean that all embodiments include the particular features,structures, and/or characteristics. Additionally, when particularfeatures, structures, and/or characteristics are described in connectionwith one embodiment, it should be understood that such features,structures, and/or characteristics may also be used connection withother embodiments whether or not explicitly described unless clearlystated to the contrary.

The following detailed description should be read with reference to thedrawings in which similar elements in different drawings are numberedthe same. The drawings, which are not necessarily to scale, depictillustrative embodiments and are not intended to limit the scope of theinvention.

A variety of pacing devices may be utilized a part of a comprehensiveplan for cardiac rhythm management. Generally, these devices may includea lead that can be implanted within target tissue within the heart suchas epicardial and/or myocardial tissue. The lead may be connected to animplantable pacemaker that provides a pacing signal to the lead and,ultimately, the target tissue. Placement of such leads and pacemakersmay require a relatively invasive surgical procedure with a relativelyhigh level of access to the patient's heart.

FIG. 1 illustrates an implantable medical device 10. Rather than using arelatively invasive surgical procedure, medical device 10 may beimplanted using a less invasive procedure. For example, medical device10 may be implanted by gaining access to the epicardium and/or to thepericardial space of the heart. This may include gaining access to theepicardium and/or to the pericardial space through a percutaneoussub-xiphoid approach. Once the desirable access is acquired, relativelysmall, low profile leads (e.g., such as a lead 12 as shown in FIG. 1)can be implanted in any of the heart chambers (e.g., right ventricle,left ventricle, right atrium, left atrium, right atrial appendage,and/or left atrial appendage), along the transvenous system, along thecoronary sinus, etc. This may include the use of a catheter or suitabledelivery device to facilitate implantation of lead 12. Some additionaldetails regarding delivery of lead 12 are disclosed herein.

In addition to lead 12, device 10 may also include a pacing member 14coupled to lead 12. In at least some instances, pacing member 14 takesthe form of an implantable cardioverter-defibrillator, a subcutaneousimplantable defibrillator, a pacing seed, or the like. Pacing member 14is generally designed to provide electrical stimulation to cardiactissue so as to aid in pacing, deliver cardiac resynchronizationtherapy, etc. The form of pacing member 14 may vary. For example, pacingmember 14 may include housing or shell, a pulse generator (e.g.,electrical circuitry), and a power source (e.g., a battery) within thehousing to provide electrical signals to lead 12 as shown in FIG. 2.Electrical communication between pacing member 14 and lead 12 mayprovide electrical stimulation to heart tissue and/or sense aphysiological condition. In general, pacing member 14 may be designed tobe implanted subcutaneously in a patient. This may include implantingpacing member 14 percutaneously sub-xiphoid (e.g., adjacent and/or justabove the xiphoid process). Placement of pacing member 14 subcutaneouslymay be desirable for a number of reasons. For example, such placementmay allow pacing member 14 to be serviced, as needed, includingreplacing the generator, replacing or recharging the battery, or thelike. In addition, the housing may be customized for sub-cutaneousimplantation and may not require structural features that would benecessary for more invasive insertion/implantation techniques.

Pacing member 14 may include a communication module (not shown) that isdesigned to allow pacing member 14 to communicate with one or moreadditional devices. For example, pacing member 14 may include a wirelesscommunication device that allows pacing member 14 to wireless transmitand/or receive data from a suitable module. In some of these and inother instances, pacing member 14 may be designed to communicate withanother devices such as an implantable cardioverter-defibrillator, asubcutaneous implantable defibrillator, or the like, or otherimplantable medical devices. Wired connections are also contemplated.

In at least some instances, pacing member 14 is fixedly attached to lead12. In other words, pacing member 14 and lead 12 are a single integratedunit. In other instances, pacing member 14 and lead 12 may be detachablyconnected/connectable with one another. For example, lead 12 may bedetachably connected with pacing member at a lead input or plug. Thismay be desirable for a number of reasons. For example, should pacingmember 14 need to be replaced, pacing member 14 can be detached fromlead 12, removed, and a replacement pacing member 14 can be attached tolead 12. This process can be done without needing to remove or otherwiseimplant a new lead 12. Furthermore, should lead 12 need to be replaced,lead 12 can be detached from pacing member, removed, and a replacementlead 12 can be implanted. In some instances, a bifurcated joint may beused so that multiple leads 12 can be connected to a single pacingmember 14 (e.g., by connecting the bifurcated joint to a single inlineconnector on pacing member 14). In addition, pacing member 14 may have aplurality of ports so that multiple leads 12 can be attached thereto.

Lead 12 may be an epicardial lead so that lead 12 may be implantedwithin the epicardium 16 of the heart 18 of a patient 20. However, thisis not intended to be limiting. Lead 12 may also be capable of beingimplanted in myocardial tissue, in the ventricular walls, in the atrialwall and/or the atrial appendages, along the transvenous system, alongthe coronary sinus, or the like. The structure of lead 12 may also vary.In at least some embodiments, lead 12 may include one or more electrodesincluding bipolar electrodes, coil electrodes, sensors, and the like.

FIGS. 2-4 schematically illustrate an example method for implanting lead12. In general, at least some of the methods contemplated may utilize asub-xiphoid percutaneous stick in order to gain access to thepericardium and/or pericardial space so that leads (e.g., such as lead12) can be implanted. In some instances, this may include the use of anintroducer, a delivery catheter, one or more guidewires, and/or the liketo advance lead 12 toward the pericardium. An imaging/visualizationsystem (e.g., such as the SPYGLASS® direct visualization system,commercially available from Boston Scientific) may be used during theprocedure to aid in guiding lead 12 to a suitable target. In some ofthese and in other embodiments, other visualization devices may be usedincluding ultrasound devices (e.g., which may use echogenic feature ondelivery tools, a magnetic tracking system for delivery tools, Dopplerto identify blood vessels, or the like), intravascular ultrasound(IVUS), ICE® imaging devices, or the like.

The methods contemplated may allow lead 12 to be implanted in anychamber of the heart 18 including the ventricles (e.g., the leftventricle 22 or the right ventricle), the atriums, and/or the atrialappendages (e.g., the left atrial appendage 26 or the right atrialappendage 28). In the illustrations shown in FIGS. 2-4, an examplemethod for accessing the ventricles (e.g., the left ventricle 22) isdepicted. While the figures show accessing the left ventricle 22,variations to this method may also allow the right ventricle to beaccessed. Modifications to access the desired location may depend on anumber of factors including heart size, entry site location and angle,etc.

Delivery may utilize a delivery system 30. System 30 may include adelivery catheter or introducer 32 and a curved needle 34. After gainingpericardial access, curved needle 34 may be advanced through introducer32 and then “stabbed” into the epicardium and/or myocardium so as toprovide a track for lead 12. Lead 12 may then be implanted by advancinglead 12 along the track formed by needle 34 as shown in FIG. 3. This mayinclude advancing lead 12 through introducer 32 (e.g., which may be apeelable introducer), through a suitable microcatheter or microintrucer,or the like.

In at least some instances, it may be desirable to utilize an anchoringmechanism to help anchor lead 12 in place along the epicardium and/ormyocardium. In such case, the anchoring mechanism can be placed before,during, or after the track is formed by needle 34. For example, FIG. 4illustrates an anchoring member 36 that may be used to anchor lead 12.In this example, anchoring member 36 includes a tether portion 38 and ananchor portion 40. Anchor portion 40 has a T-shaped end that can providea surface to grip the surface of the tissue and substantially preventmigration of anchoring member 36. In use, lead 12 may be advanced alongtether portion 38 to a suitable location (e.g., which may be rightbehind anchor portion 40 when a unipolar/monopolar lead 12 is used orfor a bipolar lead 12 both electrodes could be closely spaced within themyocardial wall or the proximal electrode could reside on the epicardialsurface). When suitably positioned, tether portion 38 could be tied in aknot or otherwise secured so that the position of lead 12 issubstantially fixed relative to anchoring member 36. While the “T-bar”type of anchoring member 36 is illustrated, other anchoring members arecontemplated including intrinsic anchoring members secured directly tolead 12 (e.g., a helix, tines, a clip, hooks, barbs, etc.), anchoringmembers placed before or after placing lead 12, shape memory anchoringmembers that may be held in a more straightened or altered configuration(e.g., within needle 34) and then allowed to take an altered shapewithin the target tissue sufficient to anchor, or the like. In someinstances, the anchoring mechanism may include structures formed from abioabsorbable material. Accordingly, the anchoring mechanism may berelied upon for initially anchoring lead 12 but then the anchoringmechanisms degrades or absorbs over time. Therefore, after a suitableamount of time, tissue growth around lead 12 may be sufficient tomaintain lead 12 in place even in the absence of the “initial” anchoringmechanism.

In some instances, lead 12 (and/or other leads disclosed herein) mayinclude a pre-formed bend. The pre-formed bend may aid in the deliveryof lead 12, for example. The pre-formed bend may be positioned near thedistal end of the lead 12 or along other suitable locations.

For atrial lead placement, the methods for implanting lead 12 may bemodified. For example, FIG. 5 schematically illustrates that aftergaining pericardial access (e.g., using a needle to stab into thepericardium and/or a curved needle to make a curved pathway into thepericardium), delivery system 30 may be used to place a guidewire 35within the pericardial space 42. Guidewire 35 may be tracked throughpericardial space 42 to either the right or left atrial appendage. Ifdesired, a relatively small catheter (not shown) can be tracked overguidewire 35 to provide a conduit for lead 12. An imaging system 44(SPYGLASS®, ultrasound, Doppler, IVUS, or the like) may be used alongwith system 30 in order to aid in guiding of lead 12 to a suitabletarget. Lead 12 may be advanced along guidewire 35 to a target tissue.Upon reaching the target, lead 12 may be anchored using a suitableanchoring mechanism. The anchoring mechanism may be similar to anchoringmember 36, may take the form of a helix or the like secure to lead 12,etc. When securing lead 12, the anchoring mechanism may bring theelectrode(s) of lead 12 into suitable contact with the target tissue(e.g., which may be the outer surface of the atrial appendage or may bewithin cardiac tissue).

With lead 12 placed at the desired target location, a variety of pacingstrategies may be employed. For example, pacing may occur at any heartchamber or combination of heart chambers (e.g., left atrium and leftventricle, right atrium and right ventricle, etc.). Biventricular (BiV)pacing may also be utilized.

FIG. 6 schematically illustrates implantable medical device 110, whichmay be similar in form and function to other medical devices disclosedherein and which may be implanted as disclosed herein. Device 110 mayinclude lead 112 and pacing member 114. In this example, lead 112 andpacing member 114 as shown as a single, integrated structure where lead112 is directly wired with pacing member 114. In other words, lead 112is fixedly attached to pacing member 114. However, other embodiments arecontemplated where lead 112 is detachably connected to pacing member114.

As shown, lead 112 may have a lumen or passageway 146 defined at least aportion of the length thereof. Passageway 146 extends between a distalend port 148 and a proximal port 150. Proximal port 150 is positionedproximally of distal end port 148 a relatively short distance so thatpassageway is akin to a “rapid exchange” or “single operator exchange”lumen of a catheter. Accordingly, passageway 146 may be used to tracklead 112 over guidewire 135 and/or an anchoring mechanism duringimplantation of lead 112.

FIG. 7 illustrates implantable medical device 210, which may be similarin form and function to other medical devices disclosed herein. Device210 may include lead 212 and pacing member 214. In this example,passageway 246 takes the form of a closed end passageway 246 that isdefined between a closed distal end 254 and proximal port 250.Passageway 246 may be used in conjunction with a removable stylet 252.Stylet 252 can be inserted into passageway 246 and pushed distally toadvance lead 212 into position. In addition, stylet 252 may be rotatedin order to effect rotation of lead 212. In at least some embodiments,stylet 252 may include steering features so that actuation of thesteering mechanism may bend or curve stylet 252 (and, thus, lead 212)into a curved configuration. This may aid in guiding lead 212 to thedesired target location. In some of these and in other embodiments,stylet 252 may have one or more pre-formed bends (e.g., an “S” curve,sine wave shape, etc.). This may provide strain relief.

FIG. 8 illustrates implantable medical device 310, which may be similarin form and function to other medical devices disclosed herein. Device310 may include lead 312. Lead 312 may be disposed within deliverysheath or catheter 332. At the proximal end, lead 312 may be attached toa pacing member (not shown) similar to those disclosed herein. Lead 312may include a tip member 356, a cathode 358, an anode 360, and connectorwire or members 362. These structural features are just examples. Otherforms and structures are contemplated.

In at least some instances, lead 312 may include a passageway such aspassageway 146/246 on lead 112/212. Accordingly, lead 312 may beadvanced along a guidewire and/or may be pushed or guided with a stylet.In other instances, lead 312 has a body without a lumen or passageway.However, lead 312 may be oriented so that connector wires 362 are offsetfrom the central axis of lead 312. This allows for a push member 364 tobe disposed within catheter 332. Push member 364 may be utilized to pushlead 312 distally from catheter 332 during delivery of lead 312.

Lead 312 may also include anchor member 336. In this example, anchormember 336 may include a pair of tines 366. Tines 366 may take the formof metallic hooks with one or more preformed bends. In some examples,tines 366 may be formed from a nickel titanium alloy. Other materialsare contemplated including those disclosed herein. During delivery,tines 366 may be positioned so that they extend distally from tip member356 within catheter 332. Push member 364 may be used to advance lead 312within catheter 332. When doing so, tines 366 may begin to emerge fromcatheter 332 as shown in FIG. 9. The preformed bends in tines 366 maybegin to shift tines 366 proximally. If the position of lead 312 is notsatisfactory, lead 312 may be proximally retracted within catheter 332and repositioned. If the position is deemed satisfactory, lead 312 maybe advanced further as shown in FIG. 10. Again, if the position of lead312 is not satisfactory, lead 312 may be proximally retracted withincatheter 332 and repositioned. If the position is deemed satisfactory,lead 312 can be further advanced until tines 366 are completely out fromcatheter 332 and so that tines 366 may engage with target tissue 368 asshown in FIG. 11.

While tines 366 extending distally within catheter 332 are one possibleanchoring mechanism that may be used with lead 312, this is not intendedto be limiting. Other anchoring mechanisms are contemplated that vary inshape, structure, form, etc. For example, FIG. 12 illustratesimplantable medical device 410, which may be similar in form andfunction to other medical devices disclosed herein. Device 410 mayinclude lead 412 and catheter 432. Lead 412 may include tip member 456,cathode 458, anode 460, and connector wires 462. Push member 464 may bedisposed within catheter 432. Lead 412 may also include anchor member436. In this example, anchor member 436 may include a pair of tines 466oriented proximally within catheter 432. In use, push member 464 may beused in a manner similar to push member 364 to advance lead 412 out fromcatheter 432.

A number of additional anchoring mechanisms are also contemplated. Forexample, anchoring members that are intended to dig into or otherpenetrate target tissue (e.g., epicardium, myocardium, etc.) may beutilized. In addition, other structures may be disposed along the leadthat may function by stabilizing the position of the lead. For example,an expandable stent-like structure may be positioned adjacent to thedistal end of the lead that is designed to expand within and stabilizethe position of the lead. Other structures such as expandable balloons,baskets, struts, and the like are also contemplated.

FIG. 13 illustrates anchoring member 536 that may be used to secure lead512 (and/or other leads disclosed herein) within epicardium 16. In thisexample, anchoring member 536 may include a tubular body 570. Tines 566may be coupled to body 570. Tines 566 may be designed to engage targettissue (e.g., epicardium 16, myocardium, etc.) and secure tubular body570 in place. Anchoring member 536 may also include engagement members572 disposed within body 570 for engaging lead 512. In this instance,engagement members 572 are projections disposed along the interior oftubular body 570 that are capable of frictionally engaging and securinglead 512.

The materials that can be used for the various components of device 10(and/or other devices disclosed herein) may include those commonlyassociated with medical devices. For simplicity purposes, the followingdiscussion makes reference to device 10. However, this is not intendedto limit the devices and methods described herein.

Device 10 may be made from a metal, metal alloy, polymer (some examplesof which are disclosed below), a metal-polymer composite, ceramics,combinations thereof, and the like, or other suitable material. Someexamples of suitable polymers may include polytetrafluoroethylene(PTFE), ethylene tetrafluoroethylene (ETFE), fluorinated ethylenepropylene (FEP), polyoxymethylene (POM, for example, DELRIN® availablefrom DuPont), polyether block ester, polyurethane (for example,Polyurethane 85A), polypropylene (PP), polyvinylchloride (PVC),polyether-ester (for example, ARNITEL® available from DSM EngineeringPlastics), ether or ester based copolymers (for example,butylene/poly(alkylene ether) phthalate and/or other polyesterelastomers such as HYTREL® available from DuPont), polyamide (forexample, DURETHAN® available from Bayer or CRISTAMID® available from ElfAtochem), elastomeric polyamides, block polyamide/ethers, polyetherblock amide (PEBA, for example available under the trade name PEBAX®),ethylene vinyl acetate copolymers (EVA), silicones, polyethylene (PE),Marlex high-density polyethylene, Marlex low-density polyethylene,linear low density polyethylene (for example REXELL®), polyester,polybutylene terephthalate (PBT), polyethylene terephthalate (PET),polytrimethylene terephthalate, polyethylene naphthalate (PEN),polyetheretherketone (PEEK), polyimide (PI), polyetherimide (PEI),polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polyparaphenylene terephthalamide (for example, KEVLAR®), polysulfone,nylon, nylon-12 (such as GRILAMID® available from EMS American Grilon),perfluoro(propyl vinyl ether) (PFA), ethylene vinyl alcohol, polyolefin,polystyrene, epoxy, polyvinylidene chloride (PVdC),poly(styrene-b-isobutylene-b-styrene) (for example, SIBS and/or SIBS50A), polycarbonates, ionomers, biocompatible polymers, other suitablematerials, or mixtures, combinations, copolymers thereof, polymer/metalcomposites, and the like.

Some examples of suitable metals and metal alloys include stainlesssteel, such as 304V, 304L, and 316LV stainless steel; mild steel;nickel-titanium alloy such as linear-elastic and/or super-elasticnitinol; other nickel alloys such as nickel-chromium-molybdenum alloys(e.g., UNS: N06625 such as INCONEL® 625, UNS: N06022 such as HASTELLOY®C-22®, UNS: N10276 such as HASTELLOY® C276®, other HASTELLOY® alloys,and the like), nickel-copper alloys (e.g., UNS: N04400 such as MONEL®400, NICKELVAC® 400, NICORROS® 400, and the like),nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such asMP35-N® and the like), nickel-molybdenum alloys (e.g., UNS: N10665 suchas HASTELLOY® ALLOY B2®), other nickel-chromium alloys, othernickel-molybdenum alloys, other nickel-cobalt alloys, other nickel-ironalloys, other nickel-copper alloys, other nickel-tungsten or tungstenalloys, and the like; cobalt-chromium alloys; cobalt-chromium-molybdenumalloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like);platinum enriched stainless steel; titanium; combinations thereof; andthe like; or any other suitable material.

As alluded to herein, within the family of commercially availablenickel-titanium or nitinol alloys, is a category designated “linearelastic” or “non-super-elastic” which, although may be similar inchemistry to conventional shape memory and super elastic varieties, mayexhibit distinct and useful mechanical properties. Linear elastic and/ornon-super-elastic nitinol may be distinguished from super elasticnitinol in that the linear elastic and/or non-super-elastic nitinol doesnot display a substantial “superelastic plateau” or “flag region” in itsstress/strain curve like super elastic nitinol does. Instead, in thelinear elastic and/or non-super-elastic nitinol, as recoverable strainincreases, the stress continues to increase in a substantially linear,or a somewhat, but not necessarily entirely linear relationship untilplastic deformation begins or at least in a relationship that is morelinear that the super elastic plateau and/or flag region that may beseen with super elastic nitinol. Thus, for the purposes of thisdisclosure linear elastic and/or non-super-elastic nitinol may also betermed “substantially” linear elastic and/or non-super-elastic nitinol.

In some cases, linear elastic and/or non-super-elastic nitinol may alsobe distinguishable from super elastic nitinol in that linear elasticand/or non-super-elastic nitinol may accept up to about 2-5% strainwhile remaining substantially elastic (e.g., before plasticallydeforming) whereas super elastic nitinol may accept up to about 8%strain before plastically deforming. Both of these materials can bedistinguished from other linear elastic materials such as stainlesssteel (that can also can be distinguished based on its composition),which may accept only about 0.2 to 0.44 percent strain beforeplastically deforming.

In some embodiments, the linear elastic and/or non-super-elasticnickel-titanium alloy is an alloy that does not show anymartensite/austenite phase changes that are detectable by differentialscanning calorimetry (DSC) and dynamic metal thermal analysis (DMTA)analysis over a large temperature range. For example, in someembodiments, there may be no martensite/austenite phase changesdetectable by DSC and DMTA analysis in the range of about −60 degreesCelsius (° C.) to about 120° C. in the linear elastic and/ornon-super-elastic nickel-titanium alloy. The mechanical bendingproperties of such material may therefore be generally inert to theeffect of temperature over this very broad range of temperature. In someembodiments, the mechanical bending properties of the linear elasticand/or non-super-elastic nickel-titanium alloy at ambient or roomtemperature are substantially the same as the mechanical properties atbody temperature, for example, in that they do not display asuper-elastic plateau and/or flag region. In other words, across a broadtemperature range, the linear elastic and/or non-super-elasticnickel-titanium alloy maintains its linear elastic and/ornon-super-elastic characteristics and/or properties.

In some embodiments, the linear elastic and/or non-super-elasticnickel-titanium alloy may be in the range of about 50 to about 60 weightpercent nickel, with the remainder being essentially titanium. In someembodiments, the composition is in the range of about 54 to about 57weight percent nickel. One example of a suitable nickel-titanium alloyis FHP-NT alloy commercially available from Furukawa Techno Material Co.of Kanagawa, Japan. Some examples of nickel titanium alloys aredisclosed in U.S. Pat. Nos. 5,238,004 and 6,508,803, which areincorporated herein by reference. Other suitable materials may includeULTANIUM™ (available from Neo-Metrics) and GUM METAL™ (available fromToyota). In some other embodiments, a superelastic alloy, for example asuperelastic nitinol can be used to achieve desired properties.

In at least some embodiments, portions or all of device 10 may also bedoped with, made of, or otherwise include a radiopaque material.Radiopaque materials are understood to be materials capable of producinga relatively bright image on a fluoroscopy screen or another imagingtechnique during a medical procedure. This relatively bright image aidsthe user of device 10 in determining its location. Some examples ofradiopaque materials can include, but are not limited to, gold,platinum, palladium, tantalum, tungsten alloy, polymer material loadedwith a radiopaque filler, and the like. Additionally, other radiopaquemarker bands and/or coils may also be incorporated into the design ofdevice 10 to achieve the same result.

In some embodiments, a degree of Magnetic Resonance Imaging (MRI)compatibility is imparted into device 10. For example, device 10 orportions thereof, may be made of a material that does not substantiallydistort the image and create substantial artifacts (e.g., gaps in theimage). Certain ferromagnetic materials, for example, may not besuitable because they may create artifacts in an Mill image. Device 10,or portions thereof, may also be made from a material that the MRImachine can image. Some materials that exhibit these characteristicsinclude, for example, tungsten, cobalt-chromium-molybdenum alloys (e.g.,UNS: R30003 such as ELGILOY®, PHYNOX®, and the like),nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such asMP35-N® and the like), nitinol, and the like, and others.

U.S. patent application Ser. No. 14/451,586, filed Aug. 5, 2014, isherein incorporated by reference.

U.S. patent application Ser. No. 14/451,601, filed Aug. 5, 2014, isherein incorporated by reference.

U.S. patent application Ser. No. 14/451,564, filed Aug. 5, 2014, isherein incorporated by reference.

U.S. patent application Ser. No. 14/451,553, filed Aug. 5, 2014, isherein incorporated by reference.

U.S. patent application Ser. No. 14/452,654, filed Aug. 6, 2014, isherein incorporated by reference.

U.S. patent application Ser. No. 14/452,617, filed Aug. 6, 2014, isherein incorporated by reference.

U.S. patent application Ser. No. 14/452,680, filed Aug. 6, 2014, isherein incorporated by reference.

U.S. patent application Ser. No. 14/452,607, filed Aug. 6, 2014, isherein incorporated by reference.

U.S. patent application Ser. No. 14/452,641, filed Aug. 6, 2014, isherein incorporated by reference.

It should be understood that this disclosure is, in many respects, onlyillustrative. Changes may be made in details, particularly in matters ofshape, size, and arrangement of steps without exceeding the scope of thedisclosure. This may include, to the extent that it is appropriate, theuse of any of the features of one example embodiment being used in otherembodiments. The invention's scope is, of course, defined in thelanguage in which the appended claims are expressed.

What is claimed is:
 1. A method of implanting an implantable medicaldevice within a patient, comprising: implanting a lead interior of thepatient's rib cage such that a proximal end of the lead is locatedexterior of the patient's rib cage and a distal end of the lead islocated interior of the patient's rib cage, the lead including adistalmost tip and at least one electrode; and subcutaneously implantinga pacing member exterior of the patient's rib cage, the pacing memberincluding a housing, a pulse generator within the housing, and a powersource within the housing; wherein the proximal end of the lead isconnected to the pacing member exterior of the patient's rib cage;wherein the at least one electrode remains exterior of all chambers ofthe patient's heart subsequent to the completion of implanting the leadinterior of the patient's rib cage; wherein at least a portion of thepacing member extends superior of the distalmost tip of the leadsubsequent to the completion of implanting the lead interior of thepatient's rib cage and subcutaneously implanting the pacing memberexterior of the patient's rib cage.
 2. The method of claim 1, whereinthe at least one electrode comprises at least two electrodes includingbipolar electrodes.
 3. The method of claim 1, wherein the lead ispositioned in contact with an epicardium of the patient's heart.
 4. Themethod of claim 1, wherein the at least one electrode is positioned incontact with an epicardium of the patient's heart.
 5. The method ofclaim 1, wherein the lead is positioned in a pericardial space of thepatient.
 6. The method of claim 1, wherein the implantable medicaldevice, including the housing of the pacing member and the leadconnected thereto, is implanted interior of the patient's skin.
 7. Themethod of claim 1, wherein the lead includes a pre-formed bend.
 8. Themethod of claim 1, wherein the lead is advanced through a deliverycatheter.
 9. The method of claim 1, wherein the proximal end of the leadis detachably connected to a lead input of the pacing member.
 10. Themethod of claim 1, further comprising anchoring the distal end of thelead to an epicardium of the patient's heart.
 11. A method of implantingan implantable medical device within a patient, comprising: implanting alead interior of the patient's rib cage by advancing the lead along anarcuate path, the lead including at least one electrode; andsubcutaneously implanting a pacing member exterior of the patient's ribcage, the pacing member including a housing, a pulse generator withinthe housing, and a power source within the housing; wherein a proximalend of the lead is connected to a lead input of the pacing memberexterior of the patient's rib cage and a distal end of the lead islocated interior of the patient's rib cage, the distal end of the leadincluding a distalmost tip; wherein the at least one electrode remainsexterior of all chambers of the patient's heart subsequent to thecompletion of implanting the lead interior of the patient's rib cage;wherein at least a portion of the pacing member extends superior of thedistalmost tip of the lead subsequent to the completion of implantingthe lead interior of the patient's rib cage and subcutaneouslyimplanting the pacing member exterior of the patient's rib cage.
 12. Themethod of claim 11, wherein the at least one electrode comprises atleast two electrodes including bipolar electrodes.
 13. The method ofclaim 11, wherein the lead is positioned in contact with an epicardiumof the patient's heart.
 14. The method of claim 11, wherein the at leastone electrode is positioned in contact with an epicardium of thepatient's heart.
 15. The method of claim 11, wherein the lead ispositioned in a pericardial space of the patient.
 16. The method ofclaim 11, wherein the implantable medical device, including the housingof the pacing member and the lead connected thereto, is implantedinterior of the patient's skin.
 17. The method of claim 11, wherein thelead includes a pre-formed bend.
 18. The method of claim 11, wherein thelead is advanced through a delivery catheter.
 19. The method of claim11, wherein the proximal end of the lead is detachably connected to alead input of the pacing member.
 20. The method of claim 11, furthercomprising anchoring the distal end of the lead to an epicardium of thepatient's heart.